Wireless microphone transmitter



1963 P. K. ONNIGIAN ETAL 3,105,938

WIRELESS MICROPHONE TRANSMITTER Filed July 2. 1960 2 Sheets-Sheet lINVENTORS PE 75/? K. ONN/G/AN KEITH KIRSTE/N 1963 P. K. ONNIGIAN ETAL3,105,933

WIRELESS MICROPHONE TRANSMITTER Filed July 2. 1960 2 Sheets-Sheet 2 IN VEN TORS KEI TH K/PS TE/N AT TORNEVS PETER K. ONN/G/AN.

United States Patent Office 3-,lfi5,938 Patented Get. 1, 1963 3,165,938WmELESS MICROPHONE TRANSMITTER Peter K. Onnigian, 1236 40th Ave.,Sacramento, Calif., Keith Kirstein, 3351 Hoily Drive, Sacramento 21, r.Y 7

Filed Italy 2, 195$, Ser. No. $24,513 1 @laim. (Cl. 325-165) Theinvention relates to radio transmitters and, more particularly, to verysmall, portable frequency-modulated transmitters.

In the television broadcasting industry cords on microphones presentproduction problems. These problems include the use of manpower tooperate mike booms, limitations to lighting of sets, and limitations tophysical movement around a set. There are also some problems indirecting, which limit the director to medium and close shots to avoidthe boom and boom shadows.

There are currently several makes of wireless microphones on the market.Some are too bulky, being in several units, while others do not have thesound quality necessary for TV broadcasting. Interference is also aproblem with some units.

It is therefore an object of the invention to provide a wirelessmicrophone which is complete and self-sufiicient in a very smallpackage.

It is another object of the invention to provide a transmitter which iscrystal controlled.

It is a further object of the invention to provide an extremely lightand portable radio transmitter yet one which has sulficient power toovercome interference.

It is still a further object of the invention to provide a radiotransmitter which is transistorized.

It is a further object of the invention to provide a radio transmitterusing FM modulation.

It is still a further object of the invention to provide a wirelessmicrophone having an over-all response of thirty cycles to sixteenthousand cycles per second.

It is yet a further object of the invention to provide a sealedencapsulated wireless microphone which is impervious to the atmosphere.

It is still a further object of the invention to provide a radiotransmitter wherein there are no switches, controls or exterior antennaand which therefore is secure from mall-adjustment by non-technicalpersonnel.

It is yet another object of the invention to provide a radio transmitterwherein the source of electrical energy can be easily removed andreplaced in a foolproof fashion.

It is yet another object of the invention to provide a radio transmitterwherein the transmitter capsule can be divided into two parts andwherein the action of separating the two parts or joining them togetherserves to turn the unit ofi and on.

It is still another object of the invention to provide a very smalldependable radio transmitter unit which is extremely rugged and freefrom mal-function.

It is still another object of the invention to provide a generallyimproved portable radio transmitter.

Other objects together with the foregoing are attained in the followingdescription and shown in the accompanying drawings in which:

FIGURE 1 is an exploded perspective of the trans rnitter capsule and theattendant power source;

FIGURE 2 is a side elevation of the assembled unit showing in outlinethe major elements of the unit; and

FIGURE 3 is a circuit diagram of the circuitry involved in thetransmitter.

FTGURES 1 and 2 particularly emphasize the mechanical aspects of thetransmitter whereas FIGURE 3 relates to the electrical portion thereof.

While the wireless microphone of the invention is susceptible ofnumerous physical embodiments depending upon the environment andrequirements of use, considerable numbers of the herein shown anddescribed embodiment have been made, tested extensively and used,particularly in connection with TV broadcasting, and all have performedin an eminently satisfactory fashion.

The small, portable frequency-modulated transmitter of the inventioncomprises a DC. power source such as dry cells 1' and 2 and connectingwires 3, 4 and 6 terminating in male connecting pins 7, 8 and 9. Thepowersource is contained in a moulded plastic cover receptacle 1411detachable from and mating with a moulded plastic base case 102. Whenthe parts are-assembled, firm electrical and mechanical connection ismade by the friction fit of the pins 7, 8 and 9 with matching sockets193, 104- and 166 in the case 102, space for the power source beingprovided by a recess 107 molded into said case 192. The principalelectrical circuitry is cast into the case 102 after initialconstruction on an insulating board shown in outline in FIGURE 2.

The transmitter comprises radio-frequency generating means,radio-frequency amplifying and radiating means, voice-frequencyamplifying means, and means for the frequency modulation of thegenerated radio-frequency currents, all being hereinafter described indetail.

The electrical circuitry of the transmitter means comprises not only thedirect current power cells 1 and 2, connecting wires 3, 4 and 6,connecting pins 7, 8 and 9 and connecting sockets 103, 104 and 1115, butit also includes further connecting leads 11, 12 and 13, thus providingoperating power for a transistor generator of radio-frequency currents,an amplifier for the radiofrequency currents, and frequency modulationmeans for said generator means and amplifier means.

The radio-frequency generator comprises a transistor 14, a frequencydetermining piezo-electric crystal 16 connected from the base electrode15 of the transistor 14 to a circuit common 22, a bias resistor -17connected between the lead 11 and the base electrode 15, a further biasresistor 18 connected from the baseelectrode 15 to the circuit common22, a capacitor 19 connected in series with a voltage-variable capacitor21, the capacitors 19 and 21 being shunted also from the base electrode15 to the circuit common 22, and a parallel resonant circuit 23 connected from the emitter electrode 26 of the transistor 14 to the circuitcommon 22. cludes a variable capacitor 23a and an inductance 231;. Thereis also provided another parallel resonant circuit 24 connected from thecollector electrode 21) of the transistor 14 to the power source lead11. The resonant circuit 24- includes a variable capacitor 24a and ainductance 24b. Shunted across the power lead 11 and the circuit common22, at the connection of the power lead 11 to the resonant circuit 24,is a capacitor 27 for the purpose of bypassing to the circuit common 22and keeping from the DC. power sources 1 and 2 any radio-frequencyvoltages.

Inductively coupled to the inductance 24b of the reso nant circuit 24 bya coil 28 is a high frequency amplifier. This comprises a transistor 29having one lead 30 of the coil 28 connected to its base electrode 31 andhaving the remaining lead 36 of the coil 28 connected to the transistoremitter electrode 33. The wire 36 also connects with the lead 11 at thejunction of the capacitor 27 and the resonant circuit 24. A resonantcircuit 34 is connected between the collector electrode 32 of thetransistor 29 and are circuit common 22. The resonant circuit 34 has avariable capacitor 34a and has an inductance 38 wound on a cylinder offerrite material 35, the ferrite material 35 serving as a radiatingantenna for the transmitter.

The resonant circuit 23 in-.

Frequency modulation of the transmitter means is obtained through thevoltage-variable capacitor 21. The capacitor 21 undergoes an alterationin value of capacity when subjected to a change in the voltage impressedacross it. Such alteration is typical of certain semi-conductor junctiondiodes operated with a voltage applied such that there is essentially nodirect current flow through the junction diode. Further, theinstantaneous frequency of oscillation of the radio-frequency genenatoris dependent upon the value of capacity shunted across the crystal 16;Therefore, if the voltage across the capacitor 21 changes, the totalcapacity inshunt with the crystal will change joined by a lead 69 fromthe collector electrode 62 to the and the instantaneous frequency of thegenerator will change. Furthermore, if the voltage across the capacitor21 is made to change at a rate corresponding to the variation in thevoltage generated by a microphone, when in a field of sound, thefrequency of the signal of the radiofrequency generator will change at acorresponding rate. Suitable receiver means will then allow demodulationand reproduction of the original soundinduced microphone voltage.

The transmitter also includes modulating means cornprising a two-stageaudio-frequency transistor amplifier means and connecting means to thevoltage-variable capacitor 21. The first stage of the audio-frequencyamplifier comprises a microphone input connector 39, a capacitor 41 topass low frequency alternating currents and to prevent direct currentsfrom appearing at the base connector 31, and a capacitor 42 connectedfrom the base electrode 48 of an amplifier transistor 46 to the circuitcommon 22 in order to shunt any radio-frequency currents to the common22. There is also provided a bias resistor 44 connected from the Wire 12to the base electrode 48, a further bias resistor 43- connected from thebase electrode 48 to the circuit common 22 and another bias andtemperature stabilization resistor 52 connected from the emitterelectrode 49 of the transistor 46 to the circuit common 22. The resistor52 has, in shunt, a capacitor 51 for the purpose of removing alternatingcurrent from the emitter electrode 49. From the collector electrode 47of the transistor 46 a load resistor 53 is connected to the power lead12.

Coupling means for the amplified audio-frequency currents from the firstamplifier stage to a second amplifier stage comprise a capacitor 54connected between the collector electrode 47 and a base electrode 61 ofan amplifier transistor 59.

Further amplification of audio-frequency currents is provided by thesecond stage amplifier means comprising the amplifier transistor 59, abias resistor 57 connected from the base electrode 61 of the transistor59 to the power source lead 12, and a further bias resistor 56 connectedfrom the base electrode 6 1 to the circuit common 22. In addition, thereis still a further biasing and temperature stabilization resistor 64connected from the emitter electrode 63 of the transistor 59 to thecircuit common 22,

the resistor 64 having in shunt with it a bypass capacitor 66 placed toremove alternating currents from the emitter electrode 63.

Shunted from the collector electrode 62 of the transistor 59 to thecircuit common 22 is a capacitor 67. This shorts out of the modulatoramplifier, with no disturbance to audio-frequency currents, anyradio-frequency currents junction point 71 of the fixed capacitor 19 andthe voltagevariable capacitor 21. The inductor 68 acts as a block toradio-frequency currents but allows audio-frequency voltages to appearbetween the junction 71 of the capacitor 19 and the voltage-variablecapacitor 21 and common circuit 22. Also connected to the collectorelectrode 62 is a load resistor 58 having its other connection to powersource lead 12.

The transmitter, as above described, is capable of transmission of voiceand music via radio-frequency propagation, using frequency modulation ofan oscillator, the mean frequency of which is accurately controlled by apiezoelectric quartz crystal. The device is small in size, issusceptible of miniaturization, as by printed circuits, and isfool-proof as Welles being rugged and durable. It can easily be carriedon the person in close association with a personal microphone and thusdoes away with the diffioulties initially described.

What is claimed is:

A portable radio transmitter comprising:

(a) an electrical circuit including a plurality of transistors and aquartz crystal, said circuit being capable of controlling the meansignal frequency of said transmitter;

(b) a voltage variable capacitor connected with said circuit, thecapacity of said capacitor being varied with the impressed voltage, saidcapacitor being effective to vary said mean signal frequency at an audiorate;

(c) an antenna comprising a high permeability ferrite rod excited by theradio frequency energy of said transmitter to produce magneticradiation;

(d). an exteriorly smoothed plastic block halving cast entirely thereinsaid circuit, said capacitor and said antenna in fixed spatial relation,said block being provided with a recess to receive a power source;

(e) a power source disposed within said recesspand (f) a recessedplastic cap adapted to engage said block and to form therewith a smoothexteriorly uninterrupted case, said cap including a plurality of membersadapted to connect with said power source only when said cap is engagedwith said block.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Article: Radio Up Your Sleeve, pages 133-136, 248 of PopularMechanics, April 1950.

Pub. I, Transistorized Transmitter," by J. Chernof,

Radio and TV News, October 1956, pages 58-59.

Great Britain May 15, 1944

